xref: /freebsd/sbin/dumpon/dumpon.8 (revision 7f3dea244c40159a41ab22da77a434d7c5b5e85a)
1.\" Copyright (c) 1980, 1991, 1993
2.\"	The Regents of the University of California.  All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\"    notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\"    notice, this list of conditions and the following disclaimer in the
11.\"    documentation and/or other materials provided with the distribution.
12.\" 3. All advertising materials mentioning features or use of this software
13.\"    must display the following acknowledgment:
14.\"	This product includes software developed by the University of
15.\"	California, Berkeley and its contributors.
16.\" 4. Neither the name of the University nor the names of its contributors
17.\"    may be used to endorse or promote products derived from this software
18.\"    without specific prior written permission.
19.\"
20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30.\" SUCH DAMAGE.
31.\"
32.\"     From: @(#)swapon.8	8.1 (Berkeley) 6/5/93
33.\" $FreeBSD$
34.\"
35.Dd May 12, 1995
36.Dt DUMPON 8
37.Os FreeBSD 2.1
38.Sh NAME
39.Nm dumpon
40.Nd "specify a device for crash dumps"
41.Sh SYNOPSIS
42.Nm dumpon
43.Op Fl v
44.Ar special_file
45.Nm dumpon
46.Op Fl v
47.Ar off
48.Sh DESCRIPTION
49.Nm Dumpon
50is used to specify a device where the kernel can save a crash dump in
51the case of a panic.
52.Pp
53Calls to
54.Nm
55normally occur from the system multi-user initialization file
56.Pa /etc/rc ,
57controlled by the
58.Dq dumpdev
59variable in the boot time configuration file
60.Pa /etc/rc.conf .
61.Pp
62The size of the specified dump device must be at least 64 KB greater the
63size of physical memory.
64.Pp
65The
66.Fl v
67flag causes
68.Nm
69to be verbose about its activity.
70.Sh NOTES
71One of the system swap devices is usually chosen as the dump device, as
72swap devices are the most likely to have the required space at dump time.
73.Pp
74The dump device can also be specified at kernel compile time using
75the
76.Dq dumps on
77clause in the kernel configuration file (see
78.Xr config 8 ).
79This is useful when the kernel panics before multi-user mode
80is reached.  Subsequent successful invocations of
81.Nm
82will override the compiled in value.
83.Pp
84The
85.Nm
86program operates by setting the
87.Xr sysctl 3
88MIB variable
89.Dq kern.dumpdev
90to the device number of the designated
91.Ar special_file
92or to
93.Dv NODEV
94(meaning that no dumps are to be taken) if
95.Ar special_file
96is the text string:
97.Dq Li off .
98.Sh SEE ALSO
99.Xr sysctl 3 ,
100.Xr fstab 5 ,
101.Xr rc.conf 5 ,
102.Xr config 8 ,
103.Xr init 8 ,
104.Xr rc 8 ,
105.Xr savecore 8 ,
106.Xr swapon 8 ,
107.Xr panic 9
108.Sh FILES
109.Bl -tag -width "/dev/{wd,da}?s?b" -compact
110.It Pa /dev/{wd,da}?s?b
111standard swap areas
112.It Pa /etc/rc.conf
113boot-time system configuration
114.El
115.Sh BUGS
116Because the filesystem layer is already dead by the time a crash dump
117is taken, it is not possible to send crash dumps directly to a file.
118.Pp
119.Nm Dumpon
120currently allows only devices with minor number 1 to be used as dump
121devices.
122.Sh HISTORY
123The
124.Nm
125command appeared in
126.Fx 2.1 .
127